Califone-5275-tape-sm维修电路图 手册.pdf

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1、RadioFans.CN Page 2 SPECIFICATIONS Power output: Wow and Flutter: Audio Frequency Response: Signal to Noise Ratio: Mic Input: Aux Input: Aux Output: Sync Track Frequency Response: Sync Input/Output: Sync Tones: Fast Forward/Rewind Time: Speaker: Power Source: Dimensions: Weight: 2 watts continuous (

2、rms) into 9 ohms at less than 5% THD, Less than 0.22% wrms 8Hz to 10kHz +/-3dB. 45 dB minimum unweighted. 0.25 mV sensitivity, for use with microphones with impedance ratings between 50 and 5,000 ohms. 250 mV sensitivity at 15,000 ohms impedance. 500 mV from 0 dB reference tape, 250 nW/m., I,000 ohm

3、s impedance 80 Hz to 8,000Hz + / - 5 dB. 500 mV rms referred to 250 nW/m. recorded level 150 Hz Tape Stop/Restart, 1,000 Hz Slide advance. 100 seconds for C-60 cassette. 5” round. 12OV 50-60 Hz AC (240V 50-60 Hz option available) or four D-size batteries. 1 1” x 1 1” x 3 -1/2”. Approximately 6.0 Ibs

4、. DESCRIPTION OF OPERATION POWER SUPPLY Power can be supplied to the 5275 either via line cord or bat- teries. The unit comes wired for 12OVAC but the wiring can be changed to 230VAC. Contact the factory for details. Q10 is a diode-connected germanium transistor, used to keep AC-de- rived power from

5、 being fed into the batteries while offering the lowest forward voltage drop from the battery supply. D21 pre- vents battery voltage from charging C97, eliminating the possibil- ity of capacitor leakage causing the battery to rundown. SW9 switches on the power whenever the tape transport is en- gage

6、d. Thedifferent LEDs can be monitored by putting the trans- port into Play and Pause. AUDIO RECORD/PLAYBACK The use of an integrated circuit designed specifically for cassette systems considerably simplifies the circuitry necessary for re- cord and playback of audio signals in the 5275. This monolit

7、hic IC contains a preamplifier circuit, an automatic level control cir- cuit, a bridged power amplifier, and a meter drive circuit. Con- sequently, the external circuitry for the audio portion of the 5275 consists mainly of switching, equalization, and coupling. The only active devices are Q12 and Q

8、13, which mute the main amp dur- ing turn-on while the preamp voltages come up and stabilize. Q14, an Aux Out buffer, and Q18, which locks the ALC circuit off in Audio Playback. For recording, the Bias Oscillator is turned on via SW1-5 by bias- ing Q2 to saturation. This provides aground to the emit

9、ter of Ql, which starts the Bias Oscillator. With no external inputs connected to the unit, the Internal Micro- phone is automatically connected as a signal input in the Record Mode. Plugging in an Auxiliary Input disconnects the Internal Mike; connecting an External Microphone disconnects either th

10、e Internal Mike or the Aux Input. The Internal Loudspeaker is dis- connected in the Record Mode to eliminate acoustic feedback. The signal being recorded can be monitored via the External Speaker Jack by headphones or by a loudspeaker placed far enough from the signal source to prevent acoustic feed

11、back. CAUTION: Always be sure the Red Cue (Sync) Rec/Erase light is OFF when playing an audio-only tape with material recorded on both sides. When playing back prerecorded tapes, it is possible, under the following circumstances, to erase the side of the tape you are not listening to: 1. Sync Rec/Er

12、ase On 2.Erase Prevention Tab for other side is in place (affects home- made tapes: commercial tapes come with this tab removed). The reason for this is that the Sync Track recorded by the 5275 corresponds to the “other side” of a normal audio-only cassette. Thus if you take a cassette you have reco

13、rded and play it on the 5275 with the Sync Record Switch on, you will erase the side you are not listening to unless me small plastic tab at the rear right has been pushed out. If the tab has not been removed, SW8 will dose. allowing SW5 to turn on the Sync Record/Erase circuitry. Commercial tapes a

14、re not subject to this problem as they come with no tab in place. SYNCTONERECORDANDPLAYBACK The 5275 has circuitry for sensing and recording 150 Hz and 1 kHz tones for making and using ANSI Standard synchronized slide programs using one or two slide projectors or one slide pro- jector with a Sync (C

15、ue) Tone to stop the cassette motor. The fol- lowing description primarily concerns itself with the 150 Hz sens- ing circuit; the 1 kHz circuit is identical in theory, differing only in time constants, except as noted. The heart of the circuit is a twin-T network in the feedback of IC3D. This networ

16、k has medium Q and makes the IC a sensitive filter. When the Q issufficientlyincreased, the IC bewmes an os- cillator. The combination of R132 and R163 makes the network have only medium Q; when Q8 shunts R163, the circuit oscil- lates, generating a Sync Tone. RadioFans.CN Page 3 SYNC PLAYBACK SECTI

17、ON Lets follow does a prerecorded Sync Tone of 150 Hz through the unit, noting the difference between what a 150 Hz and a 1 kHz tone In the Playback Mode, RL-3 is off, leaving the Sync Track Erase and Record/Playback Heads connected as shown in the schematic. The signal comes off the head and is mix

18、ed with 2.3V DC from voltage divider RlO7, R108, R111 This DC voltage biases IC2A for midpoint operation. The signal is amplified and equalized by IC2A, further amplified by Q15, and goes through SW4-1 and the Sync Out Jack. The 2.3V DC level is present at the output of IC2A, and is fed through R128

19、 to the emitter of Q4 and through R141 to the base of Q5. SW4-1 is set to either Tape Stop or Proj 2 for Sync use; the center CM position is used when playing a standard audio tape so that a 150 Hz audio tone on the cassette will not command a Motor Stop. When an output is taken from the Sync Out Ja

20、ck, the Sync Tone does not proceed through the 5275, ensuring that a Motor Stop command can not stop the motor when a program tape is being copied. VR3 adjusts the level of the Sync signal going into the Tone Sense and Projector/Motor Control circuits. The signal is fed to the non-inverting input of

21、 IC3D, which is biased by RI20 and Rl35. The twin-T network feeds back to IC3D all but the Sync Tone. causing the Sync Tone to be greatly amplified. Q16 is on during normal playback, so the signal proceeds to a rectifier and filter circuit which turns on IC2D, a comparator with hysteresis set to tri

22、gger with any input greater than one signal diode drop (approx. 0.2V DC). At this point several things can happen in the 150 Hz circuit; in the 1 kHz circuit, Cl3 turns on RL-1, advancing Projector 1 one frame. In the 150 Hz circuit. Q6 is turned on when IC2D comes high. If ” SW4 IS in the Proj 2 po

23、sition, this turns on RL1, advancing Pro- jector 2 by one frame. If SW4 is in the Tape Stop position, Q6 brings the emitter of Q5 low in comparison with the 2.3V DC de- rived from lC2A, turning on Q5. The charge on C96 (at the motor) is then shunted to ground through RI 64, Q5, SW4, and Q6, turn- in

24、g off Q1 , and the motor stops. As the charge on C67 drops to zero volts, C102 discharges and Q16 turns off. Current flows through Q4 to the base of Q6, keeping the motor off until SW7, the Tape Stop/Restart Switch, is activated. When SW7 is activated, 5V DC is fed through D6 to the base of Q4. D25,

25、 connected from RI74 and C63 to the motor (which is now off and effectively at ground), shunts this voltage away from the 150 Hz generating circuit described in the Sync Record sec- tion below, thus keeping the motor from being turned off again during the restart process. Bringing up the base of Q4

26、turns it off, turning off Q6, turning off Q5, allowing C96 to charge, turning on Q11 and the cassette motor. Q1 6 is already turned off, so any re- maining Sync Tone on the tape can not restop the motor. The collector voltage of Q6 is pulled up by R R144and Tape Stop LED 0 D18.C C102 on Q16 i isis m

27、eanwhile slowly charging; about onesec- ond is necessary to charge this capacitor and enable the circuit to tum the motor off again. In the Playback Mode, any external Sync In is shunted to ground through Rl45, bias trap C73 and L4, and RL-3. The Sync Out Jack disconnects the sync signal from the Sy

28、nc Tone Sense cir- cuitry whenever a connector is plugged into the SyncOut Jack so that a Motor Stop command on the tape will not stop the motor while a tape is being copied. During Audio Record, a large amount of Bias frequency signal is induced in the Sync Playback head; Q17 shunts this to ground

29、in the Audio Record Mode to keep the electronics from being over- whelmed by this unwanted Bias signal. SYNC RECORD SECTION SW5 and SW6 enable the Sync (Cue) Tone Erase/Record cir- cuitry when they are closed, biasing IC2B for midpoint operation, turning on RL-3 and Dl6, and biasing Q2 into saturati

30、on, which starts the Bias Oscillator by providing a ground for the emitter of Q1. (For audio recording, the biasoscillator is turned on by SW1- 5 whether Sync Record is on or off.) SW6 is located in the tape transport, behind the right side of the cassette. It closes when the Erase Prevention Tab of

31、 the cassette is in place. (See the Cau- tion in the Audio Playback section regarding accidental erasure of prerecorded tapes.) SW5 is the front panel Sync Record Switch. When SW5 and SW6 are both closed and the transport is en- gaged. Sync Tones are recorded on the cassette whenever SW6, Slide Adva

32、nce (Proj I), or SW7, Tape Stop/Restart (or Proi 2), is closed. Sync tones are audible through the loudspeaker during the Sync Record due to magnetic coupling between the two halves of the Record/Playback Head. Lets follow the signals through the record circuitry of the 150 Hz section, noting the di

33、fferences between the 150 Hz and 1 kHz sections. The 150 Hz section is chosen for this example as it is the more complicated circuit. When RL-3 closes, its terminals 9 and 15 shunt to ground the 2.3 V DC bias on the non-inverting input of IC2A. This brings the DC level of IC2As output to ground, rem

34、oving this voltage from the emitter of Q4 and the base of Q5. As a result, the Sync Tones generated by the 150 Hz oscillator can not turn off the motor in the Sync Record Mode. When the unit is in Audio Record, magnetic coupling between the two halves of the Record Head induces a very low current 60

35、 kHz Bias voltage into the input of IC2A. Q17 shorts any resultant output to ground so that it can not be fed into the tone sense cir- cuitry. Momentary closure of Tape Stop/Restart Switch SW7 (or short- ing pins 3 and 5 of the Remote Plug via a remote control unit) ap- plies 5V DC to R174 and D8. C

36、63 makes this into a pulse which is fed through D15 and R171 into IC3C, a one-shot with about a 0.5 second on-time. The positive output from IC3C turns on Q8, shorting R163 and greatly increasing the Q of the twin-T network. turning IC3D into an oscillator. The output of IC3D goes into IC2B through

37、a mixing network and level set rheostat VR4. The output of IC2B is fed through the Sync In Jack. If no plug is in this jack, the signal proceeds through bias trap C73, L4 directly to the re- cord head. Record bias is fed to the Record head through C51 andRll4. The outputs of IC3D and IC3A are also f

38、ed into their respective rectifier networks and IC2D. It is therefore normal for Projector 1 relay RL-1 to close whenever a 1 kHz Sync Tone is recorded on the tape. If SW4 is in the Proj 2 position, RL-2 will close whenever a 150 Hz tone is recorded on the tape. When an external Sync source is used,

39、 Sync In Jack J7 prevents any internally generated tones from reaching the Record Head. External Sync In senstivity is nominally 500mV. Connecting a plug to Sync Out Jack J6 prevents Sync Tones recorded on the tape from reaching the sensing circuitry. Sync Out signals are also nominally 5OOmV. Radio

40、Fans.CN RadioFans.CN RadioFans.CN Page 6 TROUBLESHOOTING THE 5275 TROUBLESHOOTING SECTIONS The Troubleshooting Information on the following pages has been divided into three sections with subsections in order to make it easier for the techni- cian to find the particular section of interest. It is re

41、commended that the fol- lowing outline be used for troubleshooting: 1. 2. 3. 4. Try out the unit, preferably with the customers tape, until the malfunc- tion occurs. If the motor works, skip Section I, Power Supply, and go directly to the relevant section. Note that the subsections are in functional

42、 order; for instance troub- leshooting a problem with Audio Record means that Audio Playback must first be verified. The Sections are as follows: I. Power Supply and Motor IIA. Audio Playback IIIA. Sync Tone Generator IIB. Audio Record 111B. Sync Record IIIC. Sync Playback IIID. Sync and Audio Recor

43、d Directions: Follow each test in order. The correct voltage or terminal, which is located on the left side of the unit and has a waveform will lead you to the next step; an in correct rneasure- black wire connected to It. ment will lead you to the defective component(s). From Step All voltages give

44、n are nominal, and may be 10% above or 2 on, the ground connectiin is taken from the negative battery below the stated voltages. 1. POWER SUPPLY AND MOTOR RadioFans.CN Page 7 II Most of the following tests are concerned with components to outside circuitry, so improper voltages on these pins, if ex-

45、 connected to ICl. If, at any point, there is a performance ternal pads are good. suggest replacement of the IC:PINS 2, problem and all external components check good, recheck 3,4,6,8,13,17.18,19,20. the DC voltages on IC1 The following pins are all AC coupled IIA. AUDIO PLAYBACK IIB AUDIO RECORD Ra

46、dioFans.CN Page 8 Review the Sync Tone Record and Playback section of the After Step 1, the following text deals directly with the 150 Hz General Description; your troubleshooting will be facilitated section. Component designations for the 1 kHz section are in by understanding the description of ope

47、ration given there. parenthesis where the two sections have common parts. IIIA. SYNC TONE GENERATORS RadioFans.CN Page 9 RadioFans.CN Page 10 I SWITCH DESIGNATIONS TRANSISTOR FUNCTIONS Q 1 Bias Oscillator Q 2 Bias Oscillator Enable Q 3 Projector 1 Relay Drive Q 4 Motor Restart 0 5 Motor Stop Control

48、 Q 6Projector 2 Relay Drive, Motor Stop Q 7 1 kHz Oscillator Start Q 8 150 Hz Oscillator Start Q 9 5.OV DC Regulation Q10 Battery Diode Q11 Motor Supply Regulation/Shutoff Q12Power-up Audio Mute Circuit Q13Power-up Audio Mute Circuit Q14 Aux Out Buffer Q15 Sync Playback Q16Motor Restart Tone Interru

49、pt Q17 Sync Out Shunt Q18 Playback ALC Defeat SW Function SW1 REC/PLAY, shown in Play SW2 PA SW3 ALC SW4 Tape Stop/Off/Proj. 2 SW5 Sync Record/Erase SW6 Slide (1) Advance SW7 Tape Stop/Restart, Slide (2) Advance SW8 Anti-Sync Record SW9 Main Power Location Main PC Board Front Panel Front Panel Jack Panel Front Panel Front Panel Front Panel Transport, right rear Transport INTEGRATED CIRCUIT FUNCTIONS ICl TA7224P Preamp, ALC, Main Amp, Meter Drive IC2 TA75324P A:Sync Playback/EQ B:Sync Oscillator Out c:Proj 1 Drive Comparator D:Proj 2 Drive Comparator 1 kHz Filter/Oscillator 1 kHz Os